While there actually has been more on-screen, non-flashback deaths in One Piece lately, even when fake-out deaths were pretty common, at least that helped sell Ace's own death as significant as, it turns out he really was dead. Marco couldn't save him, he didn't power through it, he got wounded and died next chapter.
On the other side of things, Neiji's death felt so anticlimactic because of prior resurrections.